Evaluation of Route Changes Utilizing High-Resolution GPS Bus Transit Data

Travis B. Glick, Portland State University
Miguel Figliozzi, Portland State University

Copyright National Academy of Sciences: Transportation Research Board 2018


This study applies high-resolution archived transit data to study the effect of roadway changes using data collected before and after the completion of a project affecting transit. Methodologies are presented to compare percentile and time-of-day performance measures before and after the project. In addition, differences in travel time and travel-time variability are examined over the altered route. The case study examines one heavily used route in Portland that was recently diverted onto a newly built transit-only bridge to examine the claims that travel times would decrease and reliability would increase. The results of this study indicate that travel times increased for the majority of trips but travel-time variability during the peak period was sharply reduced. Methodologies to quantify transit performance influence transportation planning and subsequent decisions; those decisions may affect operating speeds, travel times, ridership, costs, and efficiency. Transit operations research is continually evolving with the introduction of new or improved data-collection systems. Onboard global position systems (GPS) are opening up new research opportunities to visualize and quantify transit behaviors hidden by legacy data-collection systems. High-resolution (HR) GPS data-collection is expanding analysis options when implemented. However, these data-collection systems are new, not widespread, and as a result, understudied. This study applies HR data to quantify the impact of changes to roadways as a before-and-after study. This study expands on existing systems to show applicable methodologies that quantify transit performance changes following a roadway modification in locations where transit has been traditionally excluded. The case study for this paper examines the effect of the Tilikum Crossing. This new bridge in Portland, OR is the largest vehicle-free bridge in the United States. Although it is designed for light rail, streetcar, bikes, buses, and pedestrians, personal vehicles are not permitted. TriMet, Portland’s public transportation provider, claimed the new bridge would reduce travel times and improve efficiency on routes 9 and 17. This paper examines those claims for Route 9. The bridge cost was estimated at US$134 million paid for by federal grants, OR state lottery, and TriMet revenue